Display panel or portion thereof with a graphical user interface



The sole FIGURE is a front view of a display panel or portion thereof with a graphical user interface showing our design.

The outermost broken line rectangle illustrates a display panel or portion thereof that forms no part of the claimed design. All other broken lines illustrate portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display panel or portion thereof with a graphical user interface, as shown and described. 